Device for injecting a gaseous fuel into an internal combustion engine, and also metering device and pressure regulating valve

ABSTRACT

Device for injecting a gaseous fuel into an internal combustion engine with several cylinders is provided with a vaporizer pressure regulator and metering elements for supplying the fuel from the vaporizer/pressure regulator to the inlet of the cylinders. In order to ensure a uniform supply to each cylinder, the metering elements have separate metering apertures, each of which belongs to its own cylinder, and which are connected by separate respective pipes to the cylinder. A pressure regulating valve is also provided in each pipe near the inlet of the cylinder, for the purpose of maintaining a constant pressure between the metering elements and the inlet.

BACKGROUND OF THE INVENTION

The invention relates to a device for injecting a gaseous fuel into aninternal combustion engine with several cylinders, comprising avaporizer/pressure regulator, metering means for supplying the fuel fromthe vaporizer/pressure regulator to the inlet of each cylinder, as wellas an injection valve provided in each pipe near the inlet of eachcylinder, for maintaining a constant pressure between the metering meansand each inlet. Such a device is known from Dutch Application 8,600,611.This device has a manifold header which is connected at one side to acentral supply pipe supplied by the metering means, and, at the otherside, is connected to a number of supply pipes each running to the inletof a cylinder. A pressure regulating valve, for the purpose of makingthe pressure upstream of the valve independent of the pressuredownstream of the valve, is also provided between the metering means andthe manifold header.

This known device has various disadvantages. Although the pressureregulating valve used here protects the supply pipe lying upstreamthereof as regards sudden pressure changes in the inlet manifold of theengine, response problems can still occur as a result of pressureequalization in the pipes situated between the pressure regulating valveand the inlet manifold.

It is also found to be difficult to supply all cylinders uniformly. Thesupply of the cylinders far away from the manifold header often remainslower than that of those closer to it.

SUMMARY OF THE INVENTION

The object of the invention is therefore to provide a device of the typedescribed above which does not have these disadvantages. This isachieved in that the metering means have separate metering apertures,each aperture belonging to its own cylinder and connected by means of aseparate pipe of its own to that cylinder.

Each cylinder is now supplied directly by its own metering element. Thesupply pipes for all cylinders can consequently be held separate in sucha way that the favouring of one cylinder over another largely beavoided.

Besides, the whole supply line, running from the metering element to theinlet of the cylinder in question, is not affected by pressurefluctuations in the inlet manifold. This means that virtually noresponse problems can occur.

The metering means can be designed in various ways. According to aparticularly attractive and relatively simple embodiment, provision ismade for the metering means to have two metering elements which aredisplaceable relative to each other in a virtually gastight manner, andwhich can overlap to a greater or lesser extent for determining thepassage of the metering apertures.

For an internal combustion engine, the quantity of fuel flowing throughthe engine varies roughly with the product of two parameters: the speedof rotation of the engine and the specific mass of the mixture. Thespecific mass of the mixture depends on the temperature and pressureprevailing in the inlet manifold. The metering means must therefore beregulated on the basis of these two parameters. This can be achieved ina simple manner through the fact that one element has a cylindricalspace which is connected by means of a number of slits, equal to thenumber of cylinders, to the pipes connected to the cylinders, in whichcylindrical space an externally cylindrical slide can be moved.

The slide can be controlled through being coupled to an actuatorcontrolled by a processor which can control the actuator on the basis ofthe speed of rotation of the engine. The load regulation can in thiscase be achieved through the vaporizer/pressure regulator beingconnected to the inlet manifold in such a way that a pressure change inthe inlet manifold produces a pressure change in the vaporizer/pressureregulator. The pressure change in the gas flow for the metering deviceproduces a mass change of the gas, and therefore a change in the totalquantity of gas supplied per unit time. The rate of flow also increasesbecause of the pressure change. Both effects ensure the correctmetering.

The processor primarily makes use of the speed of rotation of theengine. It is possible that the speed is not sufficient in certaincircumstances and for certain types of engine. The processor cantherefore, if desired, also control the actuator on the basis of thecooling water temperature, the pressure in the inlet manifold, thethrottle valve position, the ambient temperature and pressure, thesignals coming from the lambda sensor, and also on the basis of acharacteristics map in which characteristic engine features arerecorded.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in greater detail below on the basis ofan example of an embodiment with reference to the appended figures.

FIG. 1 shows a first block diagram of the device according to theinvention.

FIG. 2 shows a view, partially in cross-section, of, a first embodimentof the metering means according to the invention.

FIGS. 3a and 3b show respective radial and axial cross-sections of themetering means according to FIG. 2.

FIG. 4 shows a second block diagram.

FIG. 5a and 5b shows views corresponding to FIG. 3a and 3b of a secondembodiment of the metering means according to the invention.

FIG. 6 shows an injection valve for the device according to theinvention.

FIGS. 7a, 7b show views in cross-section of a complete metering device,closed and open.

FIGS. 8a, 8b and 8e show variants of the metering means shown in FIG. 4.

FIG. 9 shows a partially cut-away diagram.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The block diagram of FIG. 1 shows a gas tank 1 which is connected to avaporizer/pressure regulator 2, which is in turn connected to themetering means 3. Said metering means 3 are connected by means ofinjection pipes 4 to injection valves 5, which are disposed near thecylinder inlets of the engine 6. The metering means 3 are controlled atone side by a pneumatic regulator 7, which is connected to the enginevacuum, and also by a stepping motor which is controlled by a processor9. The processor 9 receives various signals from the engine 6, such asthe engine speed 10, the pressure in the inlet manifold 11, data fromthe lambda sensor 12, and possibly further engine data such as theengine temperature 13 and the position of the throttle valve 14.

The processor 9 can also receive signals concerning the temperature ofthe inlet air 15 and the barometric pressure 16.

The processor has a memory in which a characteristics map can be stored,relating to characteristic engine features, such as, for example, thevolumetric output. The processor 9 processes all these signals and, asstated, controls the stepping motor 8 with them.

As shown in FIG. 2, the regulator 7 is connected to a lever 17 which canpivot about a hinge point 18. Movements of the regulator 7 lead to axialdisplacements of the hollow shaft 19 which is accommodated in thehousing 20. The housing 20 has a cylindrical recess 21 in which thehollow shaft fits in a gastight manner, but in such a way that it isradially and axially displaceable.

The stepping motor 9, which is not shown in any further detail, is alsoconnected by means of lever 22 to the hollow shaft 19, and can controlthe rotary movement thereof. Thanks to the play which the drive rod 23of the stepping motor has in the jaw 24 of the lever 22, the axialmovement produced by the regulator 7 remains possible.

The housing 20 has a supply channel 25 for the gaseous fuel, while thehollow shaft 19 contains a hole 26 which in any possible rotated andaxial position of the hollow shaft 19 coincides with the connection 25.

The hollow shaft is also provided with four metering holes 27, whichmore or less coincide with four metering apertures 28 in the housing 20.Injection pipes, connected to the injection valves 5, can be connectedto the metering apertures 28 by means of the internal screw thread 29.

With reference to FIGS. 3a and 3b, it can be seen that the totalpassage, determined by each pair of apertures 27, 28, can be accuratelyregulated through axial movement, and movement in the direction ofrotation, of the hollow shaft 19 relative to the housing 20. Thequantity of gaseous fuel supplied to the injection valves 5 on the basisof the above-mentioned engine data can thus be determined.

As already mentioned, the pressures are selected in such a way that thepassage through each pair of apertures 27, 28 is supercritical.

For the sake of completeness, it is further mentioned that the deviceaccording to the invention is also suitable for single-point injection.

In the second embodiment shown in FIG. 4, the load function of theengine 6, which is connected with the pressure in the inlet manifold, iscoupled to the vaporizer/pressure regulator 2. At a higher pressure inthe inlet manifold the vaporizer/pressure regulator is in this caseopened further, so that a larger quantity of gas can flow in and thepressure downstream of the vaporizer/pressure regulator can increase.

In this second embodiment a metering means 41 of the type shown in FIGS.5a and 5b can be used. This metering means comprises a housing 42 withcylindrical bore 43, in which a pin 44 is slidable in a gastight manner.The metering apertures 45 can be opened to a greater or lesser extent byaxially shifting the said pin 44. The metering apertures 45 can berectangular. The shape need not, however, be truly rectangular. Thecorners can be, for example, rounded. The apertures can also runstepwise.

These metering apertures 45 are connected by means of pipes 46 to theinjection valves 5, as described above with reference to FIG. 1.

FIG. 6 shows in cross-section an injection valve 5 according to theinvention. The injection pipe 4 is connected to the injection valve 5.The gas pressure acts on the diaphragm 30 which fulfils the function ofvalve disc. It is connected to a plate 31. When the pressure in theinjection pipe 4 is great enough, the diaphragm 30, as a result of thepressure acting on the diaphragm, will be lifted from its seat 33. Thegaseous fuel can then flow through the aperture 34 to the cylinderinlet.

It is important here that the surface of the valve seat 33 should beconsiderably smaller than that of the diaphragm 30, so that pressurevariations in the cylinder inlet have virtually no influence on thediaphragm movements. The diaphragm 30 can also be connected to a spring(which is not shown). As a first possibility, a spring which presses theplate 31 onto the seat 33 can be chosen for this. According to a secondpossibility, a spring which pushes the diaphragm 30 away from the seat30 can be selected. In the first case, a pressure above atmosphericpressure is maintained in the injection pipe, while in the second case apressure below atmospheric pressure is maintained there.

FIG. 7a and 7b show a complete embodiment of the metering means. Themetering means comprise a housing 35, with a cylindrical internal bore36. Opening into this bore are a number of connections 37, for examplefour or six, to which the metering pipes 4 according to the precedingfigures have to be connected. The gas to be metered passes through thequick-acting dry gas valve 38 into a metering chamber indicated ingeneral by 39. This chamber is set in the cylindrical recess 36 of thehousing 35.

A piston 40, which is constantly pressed into its opened position bymeans of spring 41, is movable in the interior of the chamber 39. Inthis position it fully opens the metering slits 42. The metering slits42 form the connection between the interior of chamber 39 and theconnections 37.

The piston 40, is operated by stepping motor 67, by means of which pin65 cab be pushed out to a greater or lesser distance. The pin 65 has ahead 66 which rests against the piston 40.

As shown in FIG. 7b, the piston can be fully opened under the influenceof the spring force supplied by spring 41. The pin 65 is retracted inthis case.

The supply of gas to the housing 35 can be cut off completely by meansof the control device 46 via the dry, gas shut-off valve 38. This is anadvantage, for example, during easing off the gas. The processor 9 canbe regulated here in such a way that in that case the control means 46take the valve 38 into the fully closed position, with the result thatincomplete combustion is avoided.

Several other variants of the metering chamber 39 are shown in FIGS. 8ato 8c. In FIG. 8a slits 68 whose longitudinal sides are parts of acircle with a large radius are used. FIGS. 8b and 8c show stepwise andtapering slits 63, 64 respectively.

The diagram shown in FIG. 9 shows a general view of the installationaccording to the invention, as connected to an engine. The meteringdevice 35 shown in FIG. 7 is connected to the same number of injectionvalves 5 by means of a total of four pipes 4. The injection valves 5 arefitted on the inlet manifold 47 of the engine indicated in general by48. A throttle valve with position indicator is shown at 49. The outlet50 of the engine is also provided with a lambda sensor 51. Throttlevalve position indicator and lambda sensor are connected to amicroprocessor 52.

The inlet manifold 47 is also connected to a pressure sensor 53 formeasuring the pressure in the inlet manifold 47, which pressure sensor53 is also connected to the microprocessor 52.

The supply lines of the microprocessor are indicated by 54. Accessoriessuch as a diagnostic plug 55, an indicator lamp 56 and a fuel selectorswitch 57 are also shown on the microprocessor. With this switch 57 itis possible to change between gas running and petrol running.

Three relays 60, 59, 58 are also connected to a microprocessor 52. Theyserve to switch on and switch off the petrol injection valves when theswitch-over to gas running is being made, and to switch on meteringdevice 35 and the vaporizer/pressure regulator 61.

The vaporizer/pressure regulator 61 is also shown, connected by means ofpipe 62 to the metering device 35, and by means of compensating pipe 63to the inlet manifold 47.

I claim:
 1. Device for injecting a gaseous fuel into an internalcombustion engine having a plurality of cylinders, comprising:avaporizer/pressure regulator; means for metering for supplying fuel fromsaid vaporizer/pressurizer to an inlet of each cylinder of the pluralityof cylinders, said means for metering comprising separate meteringapertures, with each metering aperture adapted to be associated with aseparate cylinder by a separate pipe; and an injection valve in eachpipe near the inlet of each cylinder to maintain a constant pressurebetween said means for metering and each inlet.
 2. The device accordingto claim 1, wherein said means for metering and said metering aperturescomprise a first metering element including first metering apertures anda second metering element including second metering apertures, saidfirst metering element and said second metering element beingdisplaceable with respect to each other in a substantially gas-tightoverlapping manner, so that alignment of said first metering aperturesand said second metering apertures is variable.
 3. The device accordingto claim 2, wherein said first metering element comprises a cylindricalspace, said first metering apertures comprise a plurality of slits,equal to a number of cylinders, connected to the pipes connected to thecylinders, and the second metering element comprises an externallymovable cylindrical slide which is slidable in said first meteringelement.
 4. The device according to claim 3, comprising an actuatorcontrolled by a processor coupled to said externally movable cylindricalslide.
 5. The device according to claim 4, wherein said processorcontrols said actuator on a basis of speed of rotation of the engine. 6.The device according to claim 5, wherein said processor further controlssaid actuator on a basis of cooling water temperature, pressure in aninlet manifold, throttle valve position, ambient temperature andpressure, signals from a lambda sensor, and a basis of a characteristicsmap in which characteristic engine features are recorded.
 7. The deviceaccording to claim 3, wherein said vaporizer/pressurizer is connected toan inlet manifold of an internal combustion engine so that a pressurechange in the inlet manifold produces a pressure change in saidvaporizer/pressurizer.
 8. The device according to claim 7, wherein aprocessor controls an actuator coupled to said externally movablecylindrical slide on a basis of cooling water temperature, pressure inan inlet manifold, throttle valve position, ambient temperature andpressure, signals from a lambda sensor, and a basis of a characteristicsmap in which characteristic engine features are recorded.
 9. The deviceaccording to claim 3, wherein said externally movable cylindrical slideis slidable in an axial direction, and said plurality of slits arelongitudinally shaped having a greatest dimension oriented in the axialdirection.
 10. The device according to claim 9, wherein said pluralityof slits are at least partially rectangular.
 11. The device according toclaim 9, wherein said plurality of slits comprise at least one taperingpart connected to a rectangular part.
 12. The device according to claim9, wherein said plurality of slits comprise two rectangular partsconnected by a tapering part.
 13. The device according to claim 9,wherein said plurality of slits comprise three rectangular partsconnected in pairs in each case by a tapering part.
 14. The deviceaccording to claim 1, wherein said means of metering comprise aquick-acting shut-off valve for shutting off a supply of gas.
 15. Thedevice according to claim 1, wherein said injection valve comprises avalve housing containing a valve seat and a valve disk interacting withsaid valve seat, and said valve disk comprises a diaphragm positioned insaid valve housing, so that said diaphragm when under no load just restsagainst said valve seat.
 16. In combination, an internal combustionengine comprising a plurality of cylinders, and a device for injecting agaseous fuel into the internal combustion engine, said devicecomprising:a vaporizer/pressure regulator; means for metering forsupplying fuel from said vaporizer/pressurizer to an inlet of eachcylinder of the plurality of cylinders, said means for meteringcomprising separate metering apertures, with each metering apertureadapted to be associated with a separate cylinder by a separate pipe;and an injection valve in each pipe near the inlet of each cylinder tomaintain a constant pressure between said means for metering and eachinlet.
 17. The combination according to claim 16, wherein said means formetering and said metering apertures comprise a first metering elementincluding first metering apertures and a second metering elementincluding second metering apertures, said first metering element andsaid second metering element being displaceable with respect to eachother in a substantially gas-tight overlapping manner, so that alignmentof said first metering apertures and said second metering apertures isvariable.
 18. The combination according to claim 17, wherein said firstmetering element comprises a cylindrical space, said first meteringapertures comprise a plurality of slits, equal to a number of cylinders,connected to the pipes connected to the cylinders, and the secondmetering element comprises an externally movable cylindrical slide whichis slidable in said first metering element.
 19. The combinationaccording to claim 18, comprising a processor coupled to said externallymovable cylindrical slide.
 20. The combination according to claim 18,wherein said externally movable cylindrical slide is slidable in anaxial direction, and said plurality of slits are longitudinally shapedhaving a greatest dimension oriented in the axial direction.